Packing Oversized Suitcases

Standard suitcases and duffel bags can be stowed under the beds, but oversized suitcases are too thick to fit there, or in slim closets. You’ll have no place to stow them except out in the open.

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Not Prebooking Special Shore Excursions

If you know you really want to do the ship’s flightseeing excursion over the Mendenhall Glacier, or tour the Cu Chi tunnels in Vietnam, sign up online before your cruise, or the tour may be sold out once you get on board. Just remember: Some cruise lines will issue a refund if you change your mind, but others won’t—so read the fine print.

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Not Bringing Body Lotion or Hair Conditioner

Luxury lines stock all bathrooms with lots of decadent toiletries, but most major mainstream lines only provide a shampoo dispenser in the shower and a bar of soap in the bathroom. It’s up to you to pack any other products you’ll need.

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Going for the Deal Without Considering the Weather

Cruises to the Caribbean are cheaper between September and early December for a reason. It’s hurricane season, and there’s a greater chance of rain. In Alaska, fares are lower at the beginning and end of the season—May and September—but it can be snowy and muddy in May, and rainy in September. Cruising Europe during the off-season might mean fewer tourists and lower prices, but be prepared for cool temps and rougher seas.

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Booking a Weekend Cruise for Peace and Quiet

Short three- to four-night cruises to warm-weather destinations like the Bahamas, Mexico, and the Caribbean attract lots of 20-somethings looking for a party. That said, shorter cruises in Europe and Asia—or on the Disney ships—won’t have the same party vibe.

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Flying in the Same Day a European Cruise Starts

If your flight is delayed or your luggage is lost, you’ll be in a real bind if you book a night flight to Europe intending to start your cruise a few hours later. Fly in the day before to be on the safe side, and enjoy a day and night of sightseeing in the port of embarkation.

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Expecting to Stay Dry in Alaska

It rains a lot in Southeast Alaska, especially in Ketchikan, so bring an umbrella and raincoat and be prepared to do your excursions—whether hiking, kayaking, biking, or sightseeing—even in a downpour. The locals are used to the wet weather, and activities are rarely canceled. June is the driest month, but some rain is still likely.

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Booking a Cruise During School Holidays

If you don’t have kids of your own—or aren’t traveling with them—avoid summer and holiday cruises, when one-third of a ship’s passengers can be children. On the biggest ships, that means more than 1,000 kids filling the pools and hot tubs, packing playrooms, running in the hallways, and making mealtime a loud and chaotic experience.

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Assuming Everything is Included OnBoard

Even if you book your own tours and don’t plan to use the specialty restaurants, you can still expect to run a bill over the course of your cruise. For example: Except on the all-inclusive, high-end cruise lines, you’ll be charged for what you drink in your cabin, whether it’s in the mini-fridge or on your dresser. (Depending on the size, sodas and bottled water will run you about $2 to $4 each.) Some onboard activities also incur fees. Case in point: fitness classes. Years ago, they were free, but no more. Zumba® dance, spinning, boot camp, and yoga will cost you an extra $10 to $15 per session.